Explosives or blasting agents, and in particular ammonium nitrate explosives, are used for a wide variety of different industrial applications ranging from mining, to mineral exploration, to civil engineering applications. Currently, there are three major classifications of commercial explosives that are based upon ammonium nitrate. These three classes are ANFO (explosives grade ammonium nitrate prills and fuel oil), watergels (slurry explosives) and ammonium nitrate based emulsions. Each form of explosive has its own particular advantages and disadvantages.
ANFO is a low cost explosive with a low velocity of detonation and with poor water resistance. ANFO also has a relatively low density of approximately 0.85 g/cc, resulting in relatively low bulk strength. Manufacturing explosives grade ammonium nitrate prills is typically carried out in large prilling towers that create particle sizes having a Tyler screen size of approximately −8 to +30. Since the prills have a natural tendency to cake or adhere to one another, after formation the prills are typically dried and coated with various anti-caking agents to help produce a free flowing product.
Watergels are manufactured from aqueous ammonium nitrate solution with or without various explosive sensitizers. Watergels may be formed with variable densities and may have a wide range of bulk strengths. Both high and low velocity products may be manufactured that exhibit relatively good water resistance. The disadvantages of watergels lies in their high manufacturing costs, which makes them considerably more expensive than ANFO.
Emulsions, the third major class of ammonium nitrate based explosives, are also manufactured from an aqueous solution of ammonium nitrate that is sensitized with glass bubbles or microspheres, and that also contains a quantity of ANFO or ammonium nitrate prills. Emulsions may be manufactured having variable densities and with a wide range of bulk strengths. Emulsions may have high or low velocities of detonation and have excellent water resistant properties. As in the case of watergels, emulsions are expensive to manufacture resulting in pricing considerably higher than ANFO products.
Accordingly, there continues to exist a need for a low cost ammonium nitrate based explosive or blasting agent that is devoid, or generally devoid, of the disadvantages associated with ANFO while at the same time exhibits some of the advantages associated with watergels and emulsions. There is also the need for an ammonium nitrate crystal product that may be readily transported and used for the production of such a blasting agent.